Author

Curtis Scholz

Date of Award

5-2015

Document Type

Thesis - Open Access

Degree Name

Master of Science in Aerospace Engineering

Department

Graduate Studies

Committee Chair

Dr. Eric Perrell

First Committee Member

Dr. Lakshmanan Narayanaswami

Second Committee Member

Dr. William Engblom

Abstract

A capability for higher accuracy heat transfer modeling in CFD for hypersonic re-entry flows, via inclusion of thermal radiation, is sought. With temperatures reaching tens of thousands of degrees, radiation is known to be significant to chemical reaction rates and thermal boundary layer development, hence surface heat transfer and thermal ablation both to the heat shield and the backshell region of re-entry vehicles. Two current NASA solicitations seek such an improved capability relative to the Mars and Earth entry problems, as uncertainty typically leads to overdesign and excess weight. The present research develops a first physics-based “building block,” which computes thermal radiation line strength distributions for certain species of interest. The spectral data required as inputs – electronic transition rates, energies, and wavelengths – for atomic nitrogen, oxygen, and hydrogen are obtained from a database maintained by NIST. Vibrational and rotational transitions of diatomic molecules are not addressed here. Absorption and emission coefficients are computed, hence an effective radiative thermal conductivity according to Rosseland is used in the “optically thick,” or “diffusion” approximation. Absorption and emission coefficients compared respectably with other published results, discrepancies attributable to differing sources of input spectral data. The computational module was implemented in an in-house Navier-Stokes research code, and demonstrated on a 2D hypersonic flow over a blunt body. The radiative diffusion model reduced peak temperatures and thermal gradients, as expected.

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